Microelectromechanical systems (MEMS) have recently been developed as alternatives for conventional electromechanical devices such as switches, actuators, valves and sensors. MEMS are commonly made up of components between 10 to 100 micrometers in size (i.e. 0.01 to 0.1 mm) and MEMS devices may range in size from a 20 micrometers (20 millionth of a meter) to a millimeter (thousandth of a meter). MEMS devices are potentially low cost devices, due to the use of microelectronic fabrication techniques. New functionality may also be provided because MEMS devices can be much smaller than conventional electromechanical devices.
U.S. Pat. No. 5,806,152 to Saitou and Jakiela, entitled “Compliant Latching Fastener” discloses a latching fastener having cocking and triggering mechanisms. The fastener has two flexible fastening latch arms each fixed at a proximal end of the arm and having a free distal end. The two arms are located relative to each other to cooperate in grasping a structure between them. A fastener cocking mechanism is connected to the fastening latch arms for retracting the distal ends of the arms when the cocking mechanism is activated, to thereby produce a latching gap between the distal ends of the arms. A trigger mechanism is located between the fastening latch arms such that a structure guided into the latching gap can actuate the trigger, for deactivating the cocking mechanism, which in turn results in closing together of the distal ends of the fastening latch arms, to grasp the structure between them and latch the structure to the fastener. The latching fastener can be fabricated of plastic or other compliant material and is particularly well suited for fabrication as a silicon micro-fastener for micro-scale applications.
Moulton and Ananthasuresh have reported in the publication “Micromechanical devices with embedded Electro-Thermal-Compliant (ETC) actuation” Elsevier, Sensors and Actuators, A 90 (2001) 38-48, a means to achieve high actuation force using a folded beam structure, consisting of a narrow and wide beam attached to each other at both ends and connected electrically in parallel. An electrical current is made to pass through the parallel connection of beams, the electrical current being shared by the narrow and wide beams causing a differential expansion of the beams. The electro-thermal actuation is capable of one hundred times the force of electrostatically actuated devices.
It is desirable to provide a latching mechanism that exhibits high contact force in the latched position suitable for application as a high power electric switch.